India is working on this RLV-TD (Reusable Launch Vehicle Test Demonstrator) as part of its plan to develop a Two-Stage-to-Orbit launch system.

So even though the aerobody of the test system is going to look vaguely Shuttle-like, it's going to use scram propulsion to help it escape the atmosphere, rather than only hypersonic re-entry.

I've always wondered if it's feasible to have a lower rocket-stage boost quickly out of the atmosphere, accelerate to a high velocity, perform stage separation and then have the remaining hypersonic stage drop back down into the upper atmosphere to use scram propulsion to do most of the remaining required acceleration. Then from there it can use some further rocket thrust to achieve orbit. So it would almost be like skipping off the atmosphere to get to orbit, after initially clearing it.

Last edited by sanman on Tue Mar 30, 2010 1:03 am, edited 1 time in total.

So the developmental path involves testing a hypersonic upper stage boosted to hypersonic speed by a rocket. That's to test the basic principles and gain the necessary data for further development.

But the ultimate goal is to develop a TSTO where the lower stage uses hypersonic propulsion, and the upper/forward stage is rocket-powered for final ascent to orbit. I presume that stage separation would occur just beyond the upper atmosphere, with a mating section (shown in red) being discarded, allowing a more streamlined nose for the hypersonic stage to now glide back to earth.

I'm not sure who else has proposed this type of design, but it doesn't seem like the usual X-plane concept that some people dismiss.

But so why can't SpaceshipThree or SpaceshipFour be like this? If Rutan can do rockets, why can't he try doing a scramjet and then eventually combine the two?

Fantasy: imagine if the XB-70 Valkyrie had morphed into something like this! We'd all be living on the Moon by now!

On its first flight, the rocket-powered craft, shaped like an aircraft, will climb 60 km into the earth’s atmosphere and glide back to earth. Over subsequent flights, the journey into outer space will be of longer duration and distances in order to test its reliability and capability to carry satellites into orbit.

Yeah, ISRO just wants to validate the aerobody design for hypersonic regime, on that first test flight. This is just a test vehicle, and that would be the HEX experiment.

My understanding is that the next test flight would then drop a test vehicle from the underbelly of a transport aircraft, to test landing gear and autonomous landing capability. That would be the LEX experiment.

Then the next flight would be a horizontal takeoff and a horizontal landing. That would be the REX experiment.

Then finally comes the SPEX experiment, which is horizontal takeoff, hypersonic scramjet flight, and horizontal landing.

So it's HEX-LEX-REX-SPEX

Then they move on to build the AVATAR.Whatever reduces the cost to orbit.